[ci] do not assume that 'time' binary is in /usr/bin

this is not the case in nix.

nix/default.nix

@@ -140,9 +140,6 @@ pkgs.lib.makeExtensible
         buildInputs = self.buildInputs;
         opamPackages = [ "headache=1.05" ];
         outputs = [ "out" ];
-        postPatch = ''
-               patchShebangs .
-        '';
         configurePhase = ''
                unset CC
                autoconf
@@ -165,6 +162,9 @@ pkgs.lib.makeExtensible
         opamPackages = self.build-distrib-tarball.opamPackages;
         src = self.build-distrib-tarball.out ;
         outputs = [ "out" ];
+        postPatch = ''
+               patchShebangs .
+        '';
         configurePhase = ''
                unset CC
                autoconf

share/analysis-scripts/analysis.mk

@@ -84,9 +84,10 @@ define time_with_output
 endef
 endif
 else
-ifneq (,$(wildcard /usr/bin/time))
+TIMEBIN:=$(shell which -a time | grep '^/')
+ifneq (,$(TIMEBIN))
 define time_with_output
-  /usr/bin/time -f 'user_time=%U\nmemory=%M' -o "$(1)"
+  $(TIMEBIN) -f 'user_time=%U\nmemory=%M' -o "$(1)"
 endef
 else
 define time_with_output